The present invention relates to a rolling bearing unit for rotatably supporting the wheels of an automobile or the like on a suspension system. More specifically, the invention relates to a rolling bearing unit equipped with a cover at an opening on an outer ring edge.
As disclosed in Japanese Laid-Open Patent Application Publication No. 10-19912, the rolling bearing unit is structured so that a cover made of resin is attached to the outer ring edge section opening to make it difficult for muddy water or the like to enter the bearing via the opening. The cover comprises a circular plate portion for covering the outer ring edge section opening and a cylindrical portion which is fitted into the inner peripheral surface of the opening with clearance. In such a cover, when the cylindrical portion is fitted into the inner peripheral surface of the outer ring edge section opening, the cylindrical portion is deformed into a narrow end and a gap occurs between the inner peripheral surface of the opening and the outer peripheral surface of the cylindrical portion, so the function of preventing muddy water from entering the bearing may be degraded.